U.S. patent application number 11/647240 was filed with the patent office on 2007-05-10 for optical waveguide module, optical waveguide film and manufacturing method thereof.
This patent application is currently assigned to Fuji Xerox Co., Ltd.. Invention is credited to Eiichi Akutsu, Shigemi Ohtsu, Keishi Shimizu, Kazutoshi Yatsuda.
Application Number | 20070104416 11/647240 |
Document ID | / |
Family ID | 35514004 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070104416 |
Kind Code |
A1 |
Shimizu; Keishi ; et
al. |
May 10, 2007 |
Optical waveguide module, optical waveguide film and manufacturing
method thereof
Abstract
An optical waveguide module includes a light emitting element
which outputs light, a light receiving element which monitors an
output of the light emitting element, and an optical waveguide film
having a waveguide core which has a notched portion having an
optical path changing surface that changes an optical path of part
of the light. The light emitting element is coupled to an end
portion of the optical waveguide film, and the light receiving
element is provided to face a position of the optical waveguide
film from where the part of the light whose optical path has been
changed by the optical path changing surface exits.
Inventors: |
Shimizu; Keishi;
(Nakai-machi, JP) ; Ohtsu; Shigemi; (Nakai-machi,
JP) ; Yatsuda; Kazutoshi; (Nakai-machi, JP) ;
Akutsu; Eiichi; (Nakai-machi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Fuji Xerox Co., Ltd.
Tokyo
JP
|
Family ID: |
35514004 |
Appl. No.: |
11/647240 |
Filed: |
December 29, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11005077 |
Dec 7, 2004 |
7174057 |
|
|
11647240 |
Dec 29, 2006 |
|
|
|
Current U.S.
Class: |
385/14 ; 385/49;
385/89 |
Current CPC
Class: |
G02B 6/4214 20130101;
G02B 6/4246 20130101; G02B 6/02033 20130101; B29D 11/00663
20130101 |
Class at
Publication: |
385/014 ;
385/049; 385/089 |
International
Class: |
G02B 6/12 20060101
G02B006/12; G02B 6/36 20060101 G02B006/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2004 |
JP |
2004-193847 |
Claims
1. An optical waveguide module comprising: a light emitting element
which outputs light; a light receiving element which monitors an
output of the light emitting element; and an optical waveguide film
having a waveguide core in the optical waveguide film which has a
notched portion having an optical path changing surface that
changes an optical path of part of the light, wherein the light
emitting element is coupled to an end portion of the optical
waveguide film, and the light receiving element is provided to face
a position of the optical waveguide film from where the part of the
light whose optical path has been changed by the optical path
changing surface exits.
2. The optical waveguide module according to claim 1, wherein the
light emitting element is a surface emitting type light emitting
element, the optical waveguide film has an optical path changing
mirror surface on one end portion thereof, and light emitted from
the surface emitting type light emitting element is coupled to the
waveguide by way of the mirror surface.
3. The optical waveguide module according to claim 2, wherein the
optical path changing mirror surface is a 45.degree. mirror surface
formed by cutting the optical waveguide film with a dicing saw
provided with a 45.degree. blade.
4. The optical waveguide module according to claim 1, wherein the
notched portion is exposed to air.
5. The optical waveguide module according to claim 1, wherein the
notched portion is filled with a cured material of ultraviolet ray
curable resin.
6. The optical waveguide module according to claim 1, wherein the
optical path changing surface is a surface inclined at an angle of
approximately 45.degree..
7. The optical waveguide module according to claim 6, wherein the
surface inclined at an angle of approximately 45.degree. is formed
by cutting the optical waveguide film with a dicing saw provided
with a vertical cutting blade which is allowed to have the
inclination of approximately 45.degree. with respect to the optical
waveguide film.
8. An optical waveguide film comprising: a lower clad film, a
waveguide core having a notched portion having an optical path
changing surface at a portion thereof; an upper clad film, wherein
the notched portion is formed only in the waveguide core; and a
second optical path changing surface on an end face of the film.
Description
[0001] This is a divisional application of application Ser. No.
11/005,077 filed Dec. 7, 2004. The disclosure of the prior
application is hereby incorporated by reference herein in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an inexpensive waveguide
film type optical module which is formed by combining an optical
waveguide film and a light emitting element such as a VCSEL, an
optical waveguide film which is used in the waveguide film type
optical module and a manufacturing method thereof.
[0004] 2. Description Related Art
[0005] As a method for manufacturing a polymer optical waveguide,
there have been proposed (1) a method in which monomer is
impregnated into a film, a core portion is selectively exposed to
change a refractive index and the film is laminated to the core
portion (a selective polymerization method), (2) a method in which
a core layer and a clad layer are coated with a material and a clad
portion is formed using reactive ion etching (a RIE method), (3) a
method which uses a photolithography method by performing exposure
and developing using ultraviolet curable resin which is formed by
adding a photosensitive material into the inside of a polymer
material (a direct exposure method), (4) a method which utilizes
injection molding, (5) a method in which a core layer and a clad
layer are applied with a material and, thereafter, a core portion
is exposed so as to change a refractive index of the core portion
(photo bleaching method) and the like.
[0006] However, the selective polymerization method (1) has a
drawback with respect to the lamination of the film, the methods
(2), (3) become costly due to the use of the photolithography
method, and the method (4) has a drawback with respect to the
accuracy of an obtained core diameter. Further, the method (5) has
a drawback that it is difficult to obtain the sufficient difference
in refractive index between the core layer and the clad layer.
[0007] Currently, although the methods which exhibit the excellent
performance in terms of practical use are the methods (2), (3),
these methods have the above-mentioned drawbacks on cost. Further,
any one of the methods (1) to (5) is not applicable to the
formation of the polymer optical waveguide on a flexible plastic
substrate having a large area.
[0008] In view of the above circumstances, inventors of the present
invention have invented and have filed patent applications on a
manufacturing method of a polymer optical waveguide which uses a
mold as a method completely different from the above-mentioned
conventional manufacturing methods of polymer optical waveguide
(see, Japanese Patent Laid-Open Publication Nos. 2004-29507,
2004-86144, and 2004-109927). This method is extremely simple, can
be performed at a low cost, and can manufacture the polymer optical
waveguides on a mass production basis. Further, in spite of the
easiness of manufacturing, the method can manufacture the polymer
optical waveguides which exhibit a small waveguide loss and also
can easily manufacture the polymer optical waveguides having any
pattern shape provided that the mold can be formed. Still further,
although it has been difficult to form the optical waveguide on the
flexible substrate conventionally, this method has succeeded in the
formation of the optical waveguide on the flexible substrate.
[0009] Here, recently, in the IC technique and the LSI technique,
to enhance the operation speed and the integration density, the use
of optical wiring between equipments, between boards in the inside
of an equipment or in the inside of a chip in place of the electric
wiring with high density has been attracting attentions.
[0010] As an element for optical wiring, for example, an optical
element having the following constitution is described in Japanese
Patent Laid-Open Publication No. 2000-39530. That is, in this
patent document, a polymer optical waveguide having a core and a
clad which wraps the core is provided with a light emitting element
and a light receiving element in the core/clad stacking direction,
and further, includes an incident-side mirror which allows light
from the light emitting element to be incident on a core and an
exit-side mirror which allows light exited from the core to enter
into a light receiving element. In such an optical element, at
portions corresponding to an optical path from the light emitting
element to the incident-side mirror and an optical path from the
exit-side mirror to the light receiving element, the clad layer is
formed in a recessed shape so as to converge the light from the
light emitting element and the light from the exit-side mirror.
Further, an optical element having the following constitution is
described in Japanese Patent Laid-Open Publication No. 2000-39531.
That is, in this patent document, in the optical element which
allows light from a light emitting element to be incident on a core
end face of a polymer optical waveguide having a core and a clad
which wraps the core, a light incident end face of the core is
formed to have a convex shape which projects toward the light
emitting element so as to converge the light from the light
emitting element whereby the waveguide loss is suppressed.
[0011] Further, Japanese Patent Laid-Open Publication No.
2000-235127 describes an optoelectronic integrated circuit in which
a polymer optical waveguide circuit is directly assembled to an
optoelectronic fusion printed circuit board which integrates
electronic elements and optical elements.
[0012] In the above-mentioned optical wiring, it is considered that
if the above-mentioned elements could be mounted and could be
incorporated into the inside of the apparatus, the degree of
freedom in designing the assembling of the optical wiring could be
increased and, as a result, compact and small light receiving and
emitting elements could be provided.
[0013] However, the methods which have been proposed heretofore
form a 90.degree. folding mirror and hence, it is necessary to
embed a mirror portion, and it is necessary to perform the highly
accurate alignment at the time of laminating the optical waveguide
and the light receiving and emitting elements thus giving rise to a
serious drawback that the cost for mounting is pushed up.
[0014] On the other hand, in the optical module which is served for
guiding the light of the light emitting element such as the VCSEL
or the like to a connector to be connected with an optical fiber,
an optical module of a type which couples the light through a micro
lens and a 45 degree mirror is generally used. Such a constitution,
however, requires one or two micro lenses on the
light-emitting-element side and also at least one micro lens on the
optical-fiber side whereby the cost necessary for forming the micro
lenses and for aligning the optical axes of the micro lenses are
pushed up. Further, in reflecting the light which propagates in
space on a 45.degree. mirror surface, to enhance the reflection
efficiency, it is necessary to form an aluminum film by vapor
deposition. This also pushes up the cost.
[0015] Accordingly, the optical module which uses an optical
waveguide film has been attracting attentions in view of the
lowering of the cost. This is because that when the end face of the
optical waveguide film is formed into a 45.degree. mirror surface
and is directly adhered to the planar light emitting element such
as the VCSEL or the like, the coupling which requires no micro
lenses can be realized. Here, as a method for forming the optical
waveguide film, the manufacturing method which is disclosed in the
above-mentioned patent documents (Japanese Patent Laid-Open
Publication Nos. 2004-29507, 2004-86144 and 2004-109927) is
advantageous for lowering the cost.
[0016] However, the light output of the laser element such as the
VCSEL or the like fluctuates due to an ambient temperature or the
like, for example. To obtain the stable light output, it is
necessary to monitor and feedback the light output per se. In this
respect, in case of the optical waveguide module, efforts have been
made including the provision of a branch waveguide for taking out
and monitoring a portion of the light output. When the multiple
light emitting points such as a 1.times.4 VCSEL array are used, it
is difficult to ensure spaces for arranging photo detectors for
monitoring (PD) and to connect waveguides branched to the spaces
with the photo detectors for monitoring. When the photo detectors
for monitoring are arranged on a side surface of the optical
waveguide film, for example, by branching the branch waveguides
from the waveguide which is coupled to two external light emitting
points, it is possible to easily guide a portion of the output
light to the photo detectors for monitoring. However, to branch the
branch waveguides from the waveguide which is connected with two
internal light emitting points to take out the light to the
outside, it is necessary to make the branch waveguides intersect
the external waveguide. Although a crosstalk is hardly generated
when the waveguides orthogonally intersect each other at the
intersecting portion, a slight waveguide loss is generated at the
portion with respect to the external waveguide thus giving rise to
a drawback that output characteristics differ between the inside
and the outside. In this case, when the photo detectors for
monitoring are collectively arranged outside in a 1.times.4 mode
for lowering the cost, there arises a drawback that the number of
intersections of the monitor waveguides is increased thus arising
the possibility that the loss is increased and the output
characteristics of the array waveguides differ.
SUMMARY OF THE INVENTION
[0017] The present invention has been made in view of the above
circumstances and provides an optical waveguide module which can
monitor an output from a light emitting point using the simple
constitution. Particularly, an aspect of the present invention
provides an optical waveguide module including a light emitting
element which outputs light, a light receiving element which
monitors an output of the light emitting element, and an optical
waveguide film having a waveguide core which has a notched portion
having an optical path changing surface that changes an optical
path of part of the light. The light emitting element is coupled to
an end portion of the optical waveguide film, and the light
receiving element is provided to face a position of the optical
waveguide film from where the part of the light whose optical path
has been changed by the optical path changing surface exits.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Embodiments of the present invention will be described in
detail based on the following figures, wherein:
[0019] FIG. 1A to FIG. 1D are views showing examples of an optical
waveguide module of the present invention, wherein FIG. 1A and FIG.
1B illustrate the mode in which a notched portion is exposed to air
and FIG. 1C and FIG. 1D illustrate the example in which the notched
portion is filled with a cured material of ultraviolet ray curable
resin;
[0020] FIG. 2A to FIG. 2C are views showing another example of the
optical waveguide module of the present invention, wherein FIG. 2A
is a plan view, FIG. 2B is a cross-sectional view taken along a
line X-X in FIG. 2A, and FIG. 2C is a cross-sectional view taken
along a line Y-Y in FIG. 2A;
[0021] FIGS. 3A and 3B are detailed views of a portion A in FIG.
2A; and
[0022] FIGS. 4A to 4G are conceptual views showing a manufacturing
process of an optical waveguide film.
DETAILED DESCRIPTION OF THE INVENTION
[0023] An optical waveguide module according to an aspect of the
present invention includes a light emitting element, a light
receiving element for monitoring an output of the light emitting
element (hereinafter, simply referred to as "light receiving
element for monitoring" or "light receiving element"), and an
optical waveguide film, and is characterized in that a waveguide
core in the optical waveguide film has a notched portion having an
optical path changing surface at a portion thereof which extends
from an upper surface to a lower surface thereof, the light
emitting element is coupled to an end portion of the optical
waveguide film, and the light receiving element for monitoring is
provided at a position which is below the optical waveguide film
and from which a portion of the waveguided light which has an
optical path thereof changed by the optical path changing surface
exits.
[0024] With respect to the upper surface and the lower surface of
the waveguide core, in the optical waveguide module which mounts
the light emitting element, the light receiving element for
monitoring and the optical waveguide film, a surface which is
arranged close to the light receiving element for monitoring of the
waveguide core forms the lower surface and a surface which is
arranged remote from the light receiving element for monitoring of
the waveguide core forms the upper surface (see FIG. 1).
[0025] The coupling of the end portion of the optical waveguide
film and the light emitting element is suitably selected depending
on a kind of the light emitting element. For example, when the
light emitting element is a surface emitting type light emitting
element, an optical path changing mirror surface (for example, a
45.degree. mirror surface) is formed on one end portion of the
optical waveguide film, and the end portion on which the mirror
surface is formed and the light emitting element are coupled to
each other. Further, when the light emitting element is a side
emitting type light emitting element, to enable the direct bonding
of an end face of the optical waveguide film and a side emitting
element, for example, a vertical end face is formed and the end
faces are coupled to each other.
[0026] Although the explanation is made with respect to the
following optical waveguide film which is provided with the optical
path changing mirror surface on one end portion in the optical
waveguide film described hereinafter, the present invention is not
limited to such an optical waveguide film.
[0027] The optical waveguide module of the present invention is
explained in conjunction with FIG. 1A to FIG. 1D.
[0028] First of all, in FIG. 1A and FIG. 1B, a example in which the
notched portion is exposed to or in contact with air is shown. In
FIG. 1A, numeral 10 indicates the optical waveguide film, numeral
10a indicates the optical path changing mirror surface, numeral 12
indicates a lower clad film, numeral 14 indicates the waveguide
core, numeral 16 indicates an upper clad film, numeral 18 indicates
a notched portion having an optical path changing surface, and
numeral 19 indicates an optical path changing surface. Further,
numeral 20 indicates the light emitting element, numeral 22
indicates a light emitting point, and numeral 24 indicates an
electrode. Numeral 30 indicates the light receiving element for
monitoring. The end portion of the optical waveguide film on which
the optical path changing mirror surface is formed is coupled to
the light emitting element using an adhesive agent or the like not
shown in the drawing. Further, the light receiving element for
monitoring is coupled to the lower clad film in the same manner.
Further, a dotted line indicates an optical path from the light
emitting point.
[0029] In the above-mentioned optical path changing mirror surface
10a and optical path changing surface 19, to perform the 90.degree.
optical path changing, the optical path changing mirror surface 10a
may be formed of a 45.degree. mirror surface and the optical path
changing surface 19 may be formed of a 45.degree. inclined surface.
Such a constitution is adopted in the above-mentioned example.
[0030] The light emitted from the light emitting point propagates
in the inside of the core while being guided after an optical path
thereof is changed by the 45.degree. mirror surface and most of the
light exits from another end portion of the core. However, a
portion of the light has an optical path thereof changed by the
optical path changing surface formed in the notched portion and is
received by the light receiving element for monitoring. In such an
optical waveguide module, the notched portion is formed toward the
inside of the core from a surface of the upper clad film.
Accordingly, the notched portion is exposed to or in contact with
air and hence, the refractive index difference is large whereby the
portion of the light is almost reflected and forms the monitoring
light.
[0031] In the optical waveguide film, a loss is determined based on
a rate of depth of a notched portion with respect to the core size.
For example, when the notched portion cuts into the core having a
diameter of 50 .mu.m from a surface of the upper clad film and
reaches a depth of 5 .mu.m of the core upper portion, the loss
attributed to the notch structure can be suppressed to
approximately 10%.
[0032] Further, the notched portion may be formed using either a
dicing saw having an extremely thin vertical cutting blade or laser
beams, for example.
[0033] An example of the above-mentioned optical waveguide module
which reduces the loss is shown in FIG. 1B. In FIG. 1B, parts
indicated by the equal symbols in FIG. 1A indicate identical
parts.
[0034] The notched portion formed in the optical waveguide module
shown in FIG. 1B is formed from the surface of the upper clad film
in the same manner as the optical waveguide module shown in FIG.
1A. However, compared to the optical waveguide module shown in FIG.
1A, an area of a notch opening portion generated by notching is
small and hence, the optical waveguide module shown in FIG. 1B has
the characteristics that the light which is not totally reflected
as the monitor light and slightly leaks although the light reaches
the notched portion can be easily taken into the waveguide
again.
[0035] Further, in FIG. 1C and FIG. 1D, an example in which the
notched portion is formed only in the waveguide core is shown. In
FIG. 1C and FIG. 1D, parts indicated by the equal symbols in FIG.
1A indicate identical parts.
[0036] The optical waveguide module shown in FIG. 1C and FIG. 1D is
formed using a mold in which the notched portion is formed in the
core at the time of manufacturing the optical waveguide film (see
the second method for manufacturing the optical waveguide film
described later) and hence, an adhesive agent or curable resin for
forming the upper clad film is filled in the notched portion during
the manufacturing step. Accordingly, compared to the case in which
the notched portion is exposed to air (FIG. 1A, FIG. 1B), the
refractive index difference with the core becomes small and hence,
the refractive index is decreased. However, by setting the
refractive index difference between the core and the upper clad
film or the adhesive agent to a suitable value, it is possible to
obtain the reflecting light for monitoring. For example, assuming a
case in which the refractive index of the core is 1.59 and the
refractive index of the adhesive agent or the upper clad film is
1.51, there exists 0.3% of the reflection of an s component (a
component having the strength of an electric field perpendicular to
an incident surface) of the light incident on the 45.degree.
surface whereby it is possible to operate the light receiving
element for monitoring with the s component.
[0037] In such a case, to increase an area of the optical path
changing surface of the notched portion by forming a notch in the
inside of the core more deeply, it is effective to form the notch
using a dicing saw provided with an extremely thin vertical cutting
blade which can form the notched portion shown in FIG. 1B. In this
case, irrespective of the depth of the notch in the inside of the
core, it is possible to form a fixed notch opening portion and
hence, the area of the opening portion is not increased even when
the deep notch is formed whereby it is possible to easily take the
light which passes through the notched portion directly into the
waveguide without scattering the light. FIG. 1D shows an example in
which such a notched portion is formed.
[0038] It is preferable to set the size (depth) of the notched
portion such that a quantity of light which has an optical path
thereof changed by the optical path changing surface is necessary
and enough to monitor using the light receiving element for
monitoring.
[0039] The quantity of light which has an optical path thereof
changed by the optical path changing surface of the notched portion
differs not only depending on the size of the optical path changing
surface but also depending on whether the notched portion is in
contact with air or is filled with the curable resin or the like.
Further, a quantity of light to be monitored also is changed
depending on the characteristics that the light receiving element
for monitoring possesses.
[0040] Accordingly, the size of the notched portion is suitably
determined by taking these factors into consideration.
[0041] Further, with respect to the position where the notched
portion is formed, to obtain a proper mode dispersion state, the
position is preferably set to a position which is slightly remote
from the light emitting point of the light emitting element as
viewed in the horizontal direction, that is, a position where the
notched portion does not extend over the optical path changing
mirror surface of the optical waveguide film. To be more specific,
it is desirable that the notched portion is positioned at a
position 1 mm or more away from the optical path changing mirror
surface as viewed in the horizontal direction. Further, in view of
the arrangement of the light receiving element for monitoring, it
is desirable that the notched portion is positioned at a position 1
mm or more away from the light emitting point.
[0042] The method for forming the notched portion is not limited
and the forming position, the size, the shape and the like of the
notched portion can be suitably selected.
[0043] In case of the above-mentioned notched portion shown in FIG.
1A, for example, it is possible to adopt a method in which the
notched portion is formed by cutting the core one time using a
dicing saw provided with a blade having a 45-degree distal end. On
the other hand, in case of the above-mentioned notched portion
shown in FIG. 1B, for example, it is possible to adopt the
above-mentioned method in which the notched portion is formed by
cutting the core one time using the dicing saw or a method which
performs the radiation of excimer laser beams one time. Both
methods can be extremely easily performed. Further, with respect to
the example shown in FIG. 1C and FIG. 1D, as will be described
later, it is possible to adopt a method in which a notched portion
is formed in a projecting portion of an original disc in an
original disc manufacturing step in manufacturing the optical
waveguide film. With respect to the method for forming the notched
portion, it is possible to use a method which is substantially
equal to the method used for forming the notched portions shown in
FIG. 1A and FIG. 1B.
[0044] As the dicing saw, for example, it is possible to use a
dicing saw DAD321 which is a product of Disco Corporation. With the
use of the dicing saw, for example, it is possible to suppress the
substantial error of the blade position within approximately 3
.mu.m. Accordingly, with respect to the waveguide core having the
size of 50.times.50 .mu.m diameter, it is possible to perform a
control to form the notch having a depth of approximately 10 .mu.m
from the upper surface of the core. Further, since the notch can be
formed uniformly in plural cores which constitute a waveguide
array, there arise no irregularities among the cores. Further, when
the notched portion is formed using such a method, even when a clad
material flows into the notched portion, a rate of scattering the
transmitting light can be decreased thus giving rise to an
advantageous effect that the loss is decreased.
[0045] Next, still another example of the optical waveguide module
of the present invention is explained in conjunction with FIG. 2A
to FIG. 2C. FIG. 2A to FIG. 2C show one example of an optical
waveguide module to which a connector for connecting a guided wave
exit end portion of the optical waveguide film to another element
(for example, an optical fiber), for example, a connector which has
interchangeability with a commercially available MT connector is
coupled. FIG. 2A is a plan view, FIG. 2B is a cross-sectional view
taken along a line IIB-IIB in FIG. 2A, and FIG. 2C is a
cross-sectional view taken along a line IIC-IIC in FIG. 2A. In FIG.
2A to FIG. 2C, numeral 10 indicates an optical waveguide film,
numeral 10a indicates a 45.degree. mirror surface, numeral 14
indicates a waveguide core, numeral 20 indicates a light emitting
element, numeral 30 indicates a light receiving element, numeral 40
indicates a ceramic package, numeral 42 indicates an electrode, and
numeral 44 indicates an electrode pin. Numeral 60 indicates a
connector, and numerals 62, 64 indicate holes formed in the
connector 60 for aligning with a connector (not shown in the
drawing) formed in another element (for example, an optical fiber).
Although not shown in the drawing, an electrode 24 (see FIG. 3) of
the light emitting element 20 is connected with the electrode 42 in
the ceramic package.
[0046] Further, FIG. 3A and FIG. 3B are detailed views which
enlarge a portion A in FIG. 2A, wherein FIG. 3A is a plan view and
FIG. 3B is a cross-sectional view taken along a line IIB-IIB in
FIG. 2A. In FIG. 3A and FIG. 3B, numeral 14 indicates a waveguide
core, numeral 18 indicates a notched portion formed in an optical
waveguide film, numeral 22 indicates a light emitting point of a
light emitting element, and numeral 24 indicates an electrode of
the light emitting element.
[0047] In this optical waveguide module, the light emitting
element, the optical waveguide film and the light receiving element
are formed on a ceramic package. The light emitting element and the
light receiving element are bonded to the ceramic package using an
adhesive agent or the like and, at the same time, the light
emitting element and an end portion (45.degree. mirror surface
forming end portion) of the optical waveguide film are bonded to
each other using an adhesive agent or the like. Here, the optical
waveguide film and the light receiving element are aligned in a
state that light from the light emitting point of the light
receiving element is incident on the optical path changing mirror
surface of the optical waveguide film. Further, the light receiving
element is arranged at a position where a reflection light from an
optical path changing surface of the notched portion formed in the
optical waveguide film is incident.
[0048] As the light emitting element, from a viewpoint of bonding
the light emitting element with the end portion of the optical
waveguide film by adhesion, a surface emitting type light emitting
element is preferably used. Further, a VCSEL, an LED and the like
are named as the surface emitting type light emitting element.
Further, as the light receiving element for monitoring, from a
viewpoint of boding the light receiving element with the lower clad
film of the optical waveguide film by adhesion, a flat type light
receiving element is preferably used. As the flat type light
receiving element used for monitoring, a Pin photo diode, an
avalanche photo diode and the like can be named.
[0049] The optical waveguide film used in the optical waveguide
module includes, as shown in FIG. 1, the lower clad film, the
waveguide core, the upper clad film and the notched portion,
wherein the "lower clad film" indicates a clad arranged close to
the light receiving element for monitoring of the optical waveguide
module.
[0050] The optical waveguide film may be formed in accordance with
the following steps, for example. Here, to facilitate the
explanation, in the explanation of the first method, the clad film
on which the core is formed in the following step 3) is used as the
"lower clad film" and the clad film which is stacked on a core
forming surface in the following step 5) is used as the "upper clad
film". However, it is needless to say that the clad film in the
step 3) constitutes the "upper clad film" in the optical waveguide
film of the present invention and the clad film in the step 5)
constitutes the "lower clad film". (In the second method, the clad
film used in the step 3) constitutes the "lower clad film").
[0051] The method including the following steps is preferably used
for manufacturing the optical waveguide film in the example shown
in FIG. 1A and FIG. 1B.
[0052] 1) a step of preparing a mold which is formed of a cured
layer of a curable resin for forming a mold and is provided with a
recessed portion corresponding to a convex portion of the waveguide
core and two or more through holes which are respectively
communicated with one end and another end of the recessed
portion;
[0053] 2) a step of bringing a lower clad film having favorable
close contact characteristics with the mold into close contact with
the mold;
[0054] 3) a step of filling the through hole formed in one end of
the recessed portion of the mold which is brought into close
contact with the lower clad film with curable resin for forming a
core and filling the recessed portion of the mold with the
core-forming curable resin by performing vacuum suction of the
core-forming curable resin from the through hole formed in another
end of the recessed portion of the mold;
[0055] 4) a step of curing the core-forming curable resin and
peeling off the mold from the lower clad film;
[0056] 5) a step of forming an upper clad film on the lower clad
film on which a core is formed; and
[0057] 6) a step of forming a notched portion having an optical
path changing surface at a portion of the waveguide core from a
surface of the upper clad film.
[0058] The steps 1) to 5) out of the above-mentioned manufacturing
steps of the optical waveguide film are explained hereinafter in
conjunction with FIG. 4. For facilitating the explanation, the
explanation is made with respect to the case in which one waveguide
core is used. FIG. 4A shows an original disc 100, wherein numeral
120 indicates a convex portion corresponding to a waveguide core.
Mold-forming curable resin is applied to or formed by molding on a
convex portion forming surface of the original disc 100 and,
thereafter, is cured (see FIG. 4B). In FIG. 4B, numeral 200a
indicates a cured resin layer. Thereafter, when the cured resin
layer 200a is peeled off, the cured resin layer 200a in which the
recessed portion is formed is obtained (not shown in the drawing).
In the cured resin layer 200a in which the recessed portion 220 is
formed, through holes 260, 280 which are communicated with the
recessed portion 220 are formed by blanking both end portions of
the recessed portion or the like whereby a mold 200 is obtained
(see FIG. 4C).
[0059] Next, as shown in FIG. 4D, the lower clad film 300 is
brought into close contact with the mold. Thereafter, core-forming
curable resin is filled into the through hole 260 formed in the
mold, and the core-forming curable resin is sucked under a reduced
pressure from the through hole 280 formed in another end so as to
fill the core-forming curable resin into the recessed portion 220
of the mold. Thereafter, the resin is cured and the mold is removed
to form, as shown in FIG. 4E, an optical waveguide core 320 on a
lower clad film 300.
[0060] Thereafter, the upper clad film 400 is formed (see FIG. 4F)
and, finally, resin portions which are cured in the inside of the
through holes 260 and 280 are cut off using a dicer to form the
optical waveguide film 10 (see FIG. 4G).
[0061] Next, the respective steps are explained.
[0062] 1) a step of preparing a mold which is formed of a cured
layer of a mold-forming curable resin and is provided with a
recessed portion corresponding to a convex portion of the waveguide
core and two or more through holes which are respectively
communicated with one end and another end of the recessed
portion.
[0063] Although it is preferable to manufacture the mold using the
original disc on which a convex shape portion corresponding to an
optical waveguide core is formed, the manufacture of the mold is
not limited to such a method. Hereinafter, the method which uses
the original disc is explained.
[0064] In the manufacture of the original disc on which the convex
portion corresponding to the optical waveguide core is formed, it
is possible to use the conventional method, for example, the
photolithography method without any particular limitation. Further,
a method which manufactures a polymer optical waveguide by an
electro-deposition method or a photo-electro-deposition method
(Japanese Patent Laid-Open Publication No. 2002-333538) is also
applicable to the manufacture of the original disc. The size of the
convex portion corresponding to the optical waveguide formed on the
original disc is suitably determined corresponding to the
application or the like of the polymer optical waveguide. For
example, in case of the optical waveguide for a single mode, a core
having about 10 .mu.m square is used, while in case of the optical
waveguide for a multiple mode, a core having about 50 to 100 .mu.m
square is generally used. According to the application, it is
possible to make use of an optical waveguide having a still larger
core portion having several hundred .mu.m square.
[0065] As an example of the manufacture of the mold, it is possible
to name a method in which on the convex portion forming surface of
the original disc formed in the above-mentioned manner, a layer
made of mold-forming curable resin is formed by a method which
applies or forms the mold-forming curable resin by molding and,
thereafter, when necessary, the dry treatment is performed and the
curing treatment is performed and, thereafter, the cured resin
layer is peeled off from the original disc and takes a mold in
which the recessed portion corresponding to the convex portion is
formed, and the through holes which are respectively communicated
with one end and another end of the recessed portion are formed in
the mold. The communication holes are formed by blanking the mold
in a given shape, for example. Even when the through holes are
formed by blanking, the mold and the clad film substrate are
favorably brought into contact with each other and hence, no gap is
formed between the mold and the lower clad film besides the
recessed portion of the mold whereby there is no possibility that
the core-forming curable resin penetrates other than the recessed
portions.
[0066] Although a thickness of the mold (layer of cured resin) is
suitably determined by taking the handling property of the mold
into consideration, it is generally proper to set the thickness to
approximately 0.1 to 50 mm.
[0067] Further, it is preferable to perform the mold removing
treatment such as applying of a mold peeling agent to the original
disc in advance to enhance the peeling off the original disc from
the mold.
[0068] The through hole on the core-forming curable resin filling
side has a reservoir of liquid (core-forming curable resin).
Further, the through hole formed on the core-forming curable resin
discharging side is used for performing the suction under reduced
pressure to reduce the pressure inside the recessed portion of the
mold at the time of filling the recessed portion of the mold with
the resin. The shape and the size of the filling-side through hole
are not limited particularly, provided that the through hole is
communicated with the filling end of the recessed portion and has a
function of serving as a reservoir of liquid. The shape and the
size of the discharge-side thorough hole are not limited
particularly, provided that the discharge-side through hole is
communicated with the discharge end of the recessed portion and is
used for the suction under reduced pressure.
[0069] Since the through hole formed on the core-forming curable
resin filling side of the recessed portion of the mold has a
function of the liquid reservoir, when the mold is brought into
close contact with the lower clad film, by allowing a
cross-sectional area of the through hole to become large on a side
that the through hole is brought into contact with the substrate
and to become small as the through hole is spaced apart from the
substrate, it is possible to easily peel off the mold from the
substrate after filling and curing the core-forming curable resin
into the recessed portion. It is unnecessary to provide the liquid
reservoir function to the through hole formed on the core-forming
curable resin discharging side, hence it is unnecessary for the
through hole formed on the core-forming curable resin discharging
side to adopt such a constitution.
[0070] Further, as another example of manufacturing the mold, it is
possible to name a method in which not only the convex portion
corresponding to the optical waveguide core but also a convex
portion for forming the through hole (a height of the convex
portion being set greater than a thickness of the cured layer of
the mold-forming curable resin) are formed in the original disc,
the mold-forming curable resin is applied to the original disc in a
state that the convex portion for forming the through hole
penetrates the resin layer and, then, the resin layer is cured and,
thereafter, the cured resin layer is peeled off from the original
disc.
[0071] It is preferable that the mold-forming curable resin used in
the manufacture of the mold has properties that the cured material
can be easily peeled off from the original disc, the cured material
has fixed or more mechanical strength and size stability required
as a mold (for the repeated use), the cured material has hardness
(the degree of hardness) for maintaining the recessed shape, and
the good close contact property with the lower clad film. It is
preferable to add various additives to the mold-forming curable
resin when necessary.
[0072] The mold-forming curable resin is required to be applied to
or molded on the surface of the original disc and, at the same
time, is required to accurately copy convex portions formed on the
original disc corresponding to respective optical waveguide cores
and hence, it is preferable that the mold-forming curable resin has
the viscosity of a certain limit or less, for example,
approximately 500 to 700 mPas. (Here, the "mold-forming curable
resin" used in this specification includes resin which becomes a
rubber-like body having resiliency after curing). Further, it is
possible to add a solvent for viscosity adjustment to the
mold-forming curable resin to an extent that the solvent does not
adversely influence the mold-forming curable resin.
[0073] The mold-forming curable resin preferably uses curable-type
organo-poly-siloxane which constitutes silicone rubber (silicone
elastomer) or silicone resin after curing from a viewpoint of the
above-mentioned peeling property, the mechanical strength, the size
stability, the hardness, the close contact property with the clad
substrate. It is preferable that the curable-type
organo-poly-siloxane includes a methyl-siloxane group, an
ethyl-siloxane group, and a phenyl-siloxane group in molecules
thereof. The curable organo-poly-siloxane may be either a
one-component type or a two-component type which is used in
combination with a curable agent. Further, the curable
organo-poly-siloxane may be a thermosetting type or a
room-temperature curing type (cured with moisture in air, for
example). Still further, the curable organo-poly-siloxane may make
use of other curing method (ultraviolet ray curing or the
like).
[0074] As the curable organo-poly-siloxane, it is preferable to use
curable organo-poly-siloxane which becomes silicone rubber after
curing. As the curable organo-poly-siloxane, the silicone rubber
which is usually referred to as the liquefied silicone rubber
(including the curable organo-poly-siloxane in a paste form having
high viscosity) is used. It is preferable to use a two-liquid type
which is used in combination with a curing agent. Particularly,
with respect to the addition-type silicone rubber in a liquefied
form, it is possible to cure both of a surface and the inside
thereof uniformly in a short period. Further, since a byproduct is
not produced or hardly produced at the time of curing and hence,
the addition-type silicone rubber in a liquefied form exhibits the
excellent peelability and a small contraction rate.
[0075] With respect to the above-mentioned liquefied silicone
rubber, it is preferable to use the liquefied di-methyl-siloxane
rubber in view of the close contacting property, the peelability,
the strength and the hardness. Further, the cured material of the
liquefied di-methyl-siloxane rubber generally has the low
refractive index of approximately 1.43 and hence, the mold which is
formed of the liquefied di-methyl-siloxane rubber is not peeled off
from the clad substrate and can be preferably directly used as the
upper clad film. In this case, it is necessary to provide the
constitution which prevents the mold, the filled core forming resin
and the clad substrate from being peeled off from each other.
[0076] The viscosity of the liquefied silicone rubber is, from a
viewpoint of accurately copying the convex portions corresponding
to the optical waveguide cores and of easing the defoaming by
reducing the mixing of bubbles and a viewpoint of manufacturing the
mold having a thickness of several mm, preferably set to
approximately 500 to 7000 mPas, and more particularly to
approximately 2000 to 5000 mPas.
[0077] A surface energy of the mold is set to 10 dyn/cm to 30
dyn/cm, and more preferably to 15 dyn/cm to 24 dyn/cm in view of
the close contact property with the substrate film.
[0078] The Shore hardness of the mold is set to 15 to 80, and more
preferably to 20 to 60 from viewpoints of mold forming performance,
the maintenance of the shape of the recessed portion and the
peelability.
[0079] The surface roughness of the mold (square mean value
roughness (RMS)) is preferably 0.2 .mu.m or less, and more
preferably 0.1 .mu.m or less in view of the mold forming
performance.
[0080] Further, it is preferable that the mold has the light
transmitting property in the ultraviolet ray region and/or in the
visible light region. The reason that it is preferable to provide
the light transmitting property to the mold in the visible light
region is that the alignment can be easily performed at the time of
bringing the mold into close contact with the lower clad film in
the following step 2) and the manner in which the recessed portion
of the mold is filled with the core-forming curable resin can be
observed in the following step 3) whereby the completion of the
filling operation can be easily confirmed. Further, the reason that
it is preferable to provide the light transmitting property to the
mold in the ultraviolet ray region is that when ultraviolet ray
curable resin is used as the core-forming curable resin, it is
possible to perform the ultraviolet ray curing through the mold
whereby it is preferable that the transparency of the mold in the
ultraviolet ray region (250 nm to 400 nm) is 80% or more.
[0081] The curable-type organo-poly-siloxane, particularly, the
liquefied silicone rubber which becomes silicone rubber after
curing exhibits both of the excellent close contact property with
the lower clad film and the excellent peelability which contradict
each other and hence, has the ability to copy the nano-structure
whereby by bringing the silicone rubber into close contact with the
lower clad film, it is possible to prevent the intrusion of liquid.
The mold which uses such silicone rubber can accurately copy the
original disc and is favorably brought into contact with the lower
clad film and hence, it is possible to efficiently fill the core
forming resin only in the recessed portion between the mold and the
lower clad film and, at the same time, the peeling off of the mold
from the lower clad film can be facilitated. Accordingly, it is
possible to extremely easily manufacture the polymer optical
waveguide which maintains the shape with high accuracy from the
mold.
[0082] 2) the step of bringing a lower clad film having favorable
close contact characteristics with the mold into close contact with
the mold.
[0083] The optical element which is formed of the polymer optical
waveguide of the present invention is used in the light wiring in
various layers and hence, the material of the lower clad film is
selected by taking optical characteristics such as the refractive
index, the optical transparency or the like, the mechanical
strength, the heat resistance, the close contact property with the
mold, the flexibility and the like into consideration depending on
the usage of the optical element. Further, to take out the monitor
light from the lower clad film, it is necessary to allow the lower
clad film to have the optical transparency.
[0084] As the above-mentioned film, a cycloaliphatic acrylic resin
film, a cycloaliphatic olefin resin film, a cellulose tri-acetate
film, a fluororesin film or the like can be named. It is desirable
that the refractive index of the film substrate is set to a value
smaller than 1.55, and preferably to a value smaller than 1.52 to
ensure the refractive index difference with the core. It is
preferable that the lower clad film has the resiliency.
[0085] As the above-mentioned cycloaliphatic acrylic resin film,
OZ-1000 or OZ-1100 (made by Hitachi Chemical Co., Ltd.) which
incorporates aliphatic cyclic hydrocarbon of tricyclodecane or the
like in an ester substituent is used.
[0086] Further, as the cycloaliphatic olefin resin film, the resin
film having the norborne structure in a principal chain, and the
resin film having the norborne structure in a principal chain and a
polar group such as alkyloxycarbonyl group (alkyl group having the
carbon number of 1 to 6 or a cycloalkyl group) in side chains are
named. Particularly, the cycloaliphatic olefin resin having the
norborne structure in a principal chain and a polar group such as
alkyloxycarbonyl group in side chains has the excellent optical
characteristics such as the low refractive index (the refractive
index being around 1.50 thus ensuring the difference in refractive
index between the core and the clad) and the high optical
transparency and the like, exhibits the excellent close contact
property with the mold, and also exhibits the excellent heat
resistance and hence, this cycloaliphatic olefin resin film is
suitable for the manufacture of the optical waveguide sheet of the
present invention.
[0087] Further, a thickness of the lower clad film is preferably
set to at least 20 .mu.m to ease the handling at the time of
stacking and to maintain the mechanical strength imparted to the
optical waveguide film. When the film thickness is smaller than 20
.mu.m, at the time of manufacturing, a bending force is applied to
the waveguide core portion and hence, a strain is liable to be
generated in a core portion whereby a yield rate is deteriorated or
the performance is remarkably lowered. Further, from a viewpoint of
ensuring the mechanical strength of the optical waveguide film, it
is preferable to increase the thickness of the lower clad film.
[0088] On the other hand, since the lower clad film is directly
bonded to the light receiving element and the light emitting
element without passing through the micro lens and hence, the
thickness of the lower clad film directly becomes a length of an
optical path between the optical path changing mirror surface of
the optical waveguide film and the light emitting point and a
length of an optical path between a light receiving point of the
light receiving element and the optical path changing surface of
the notched portion. Accordingly, to ensure the bonding efficiency,
it is desirable that the thickness of the lower clad film remains
small. To consider that above-mentioned situation, an upper limit
of a thickness of the lower clad film is set to 200 .mu.m or less,
preferably 100 .mu.m or less, and more preferably 70 .mu.m or
less.
[0089] 3) a step of filling the through hole formed in one end of
the recessed portion of the mold which is brought into close
contact with the lower clad film with core-forming curable resin
and filling the recessed portion of the mold with the core-forming
curable resin by performing vacuum suction of the core-forming
curable resin from the through hole formed in another end of the
recessed portion of the mold.
[0090] In this step, the core-forming curable resin is filled into
the through hole formed on the resin filling portion side and,
thereafter, by performing the suction under pressure from the
through hole formed on the resin discharge side so as to fill the
core-forming curable resin into a space (the recessed portion of
the mold) which is formed between the mold and the lower clad film.
Due to the suction under the reduced pressure, the close contact
property of the mold and the lower clad film is enhanced whereby
the mixing of bubbles can be obviated. The suction under the
reduced pressure is, for example, performed by inserting a suction
pipe into the through hole formed on the discharge portion side and
by connecting the suction pipe to a pump.
[0091] As the core-forming curable resin, various kind of resin
such as the radiation beam curable resin, the electron beams
curable resin, thermosetting resin or the like can be used.
Particularly, the ultraviolet ray curable resin and the
thermosetting resin are preferably used.
[0092] Further, as the ultraviolet ray curable resin or the
thermosetting resin for forming core, ultraviolet-ray-curing or
thermosetting monomer, oligomer or the mixture of the monomer and
oligomer is preferably used.
[0093] Further, as the ultraviolet ray curable resin, epoxy-based,
polyimide-based or acrylic ultraviolet ray curable resin is
preferably used.
[0094] Since the core-forming curable resin is filled into a space
(recessed portion of the mold) formed between the mold and the
lower clad film based on capillarity, the core-forming curable
resin to be used is required to possess the sufficiently low
viscosity to enable such filling. Accordingly, the viscosity of the
curable resin is preferably set to 10 mPas to 2000 mPas, more
preferably 20 mPas to 1000 mPas, and still more preferably 30 mPas
to 50 mPas.
[0095] Besides the above-mentioned conditions, to reproduce the
original shape of the convex portion formed on the original disc
corresponding to the optical waveguide core with high accuracy, it
is necessary that a volumetric change of the curable resin before
and after curing is small. For example, when the volume is reduced,
it gives rise to a waveguide loss. Accordingly, it is preferable
that the volumetric change of the curable resin is as small as
possible. That is, the volumetric change of the core-forming
curable resin is preferably 10% or less, more preferably 6% or
less. Since the lowering of the viscosity using a solvent induces
the large volumetric change of the core-forming curable resin
before and after curing, it is preferable to obviate the use of the
solvent for lowering the viscosity.
[0096] To decrease the volumetric change (contraction) of the
core-forming curable resin after curing, polymer may be added to
the resin. The polymer may preferably be polymer which has the
compatibility with the core-forming curable resin and does not
adversely influence the refractive index, the resiliency and the
transmitting characteristics of the resin. Further, the addition of
the polymer can not only decrease the volumetric change but also
control the viscosity and a glass transfer point of the cured resin
with high accuracy. As such a polymer, for example, acrylic-based
polymer, metharylic-based polymer or epoxy-based polymer can be
used. However, the polymer is not limited to these polymers.
[0097] The refractive index of the cured material of the
core-forming curable resin is required to be greater than the
refractive index of the above-mentioned films which become clad
(including the upper clad film in the step 5) described later) and
is 1.50 or more, and preferably 1.53 or more. The difference in
refractive index between the clad (including the upper clad film in
the step 5) described later) and the core is 0.01 or more, and
preferably 0.02 or more.
[0098] 4) the step of curing the core-forming curable resin and
peeling off the mold from the lower clad film.
[0099] In this step, the filled core-forming curable resin is
cured. To cure the ultraviolet ray curable resin, an ultraviolet
ray lamp, an ultraviolet ray LED, a UV radiation device or the like
is used, while to cure the thermosetting resin, the heating of the
thermosetting resin in an oven or the like is used.
[0100] Further, the mold used in the above-mentioned steps 1) to 3)
can be directly used for forming the upper clad film provided that
the conditions such as the refractive index and the like are
satisfied. In this case, it is unnecessary to peel off the mold and
the mold can be directly utilized as the upper clad film. Further,
in this case, it is preferable to apply an ozone treatment to the
mold to enhance the adhesive property between the mold and the core
material.
[0101] 5) the step of forming an upper clad film on the lower clad
film on which a core is formed.
[0102] Although the upper clad film is formed on the lower clad
film on which the core is formed, as the upper clad film, a film
(for example, the lower clad film used in the above-mentioned step
2) being used in the same manner), a layer which is obtained by
applying and curing clad-forming curable resin, a polymer film
which is obtained by applying and drying a solution solvent of a
polymer material or the like can be named. As the clad-forming
curable resin, ultraviolet ray curable resin or thermosetting resin
is preferably used. For example, the ultraviolet ray curing or the
thermosetting monomer, oligomer or the mixture of the monomer and
oligomer is used. Although various kinds of resins including
acrylic resin, epoxy-based resin and the like exist as the
ultraviolet ray curable resin, resin which belongs to a non-solvent
based resin group and has a volume contraction rate of
approximately 4 to 5% is commercially available and obtainable.
With the use of the ultraviolet ray curable resin, it is possible
to ensure the favorable optical transparency. Although the
volumetric contraction ratio of the thermosetting resin is smaller
than the volumetric contraction ratio of the ultraviolet ray
curable resin, the optical transparency of the thermosetting resin
is generally slightly lower than the optical transparency of the
ultraviolet ray curable resin.
[0103] To reduce the volumetric change (contraction) of the
clad-forming curable resin after curing, it is possible to add
polymer (for example, methacrylic or epoxy-based polymer) which has
the compatibility with the resin and does not adversely influence
the refractive index, the elastic modulus, the transmitting
characteristics of the resin to the resin.
[0104] When a film is used as the upper clad film, the film is
laminated using an adhesive agent. Here, it is desirable that the
refractive index of the adhesive agent is close to the refractive
index of the film. As the adhesive agent to be used, the
ultraviolet ray curable resin or the thermosetting resin is
preferably used, wherein, for example, monomer, oligomer and the
mixture of the monomer and the oligomer, of the ultraviolet ray
curable resin or the thermosetting resin is used.
[0105] To decrease the volumetric change (contraction) after curing
of the ultraviolet ray curable resin or the thermosetting resin,
polymer similar to the polymer added to the upper clad film is
added to the adhesive agent.
[0106] It is desirable to set the refractive index of the upper
clad film to 1.55 or less, and more preferably to 1.52 or less to
ensure the difference in refractive index between the upper clad
film and the core. Further, it is also preferable to set the
refractive index of the upper clad film and the refractive index of
the film substrate equal to each other in view of the confinement
of light.
[0107] 6) the step of forming a notched portion having an optical
path changing surface at a portion of the waveguide core from a
surface of the upper clad film.
[0108] In this step, the notched portion having the optical path
changing surface at the portion of the waveguide core is formed in
the above-mentioned manner.
[0109] The optical waveguide film shown in FIG. 1C and FIG. 1D can
be manufactured by the method which includes the following
steps.
[0110] 1) a step of preparing a mold which is formed of a cured
layer of a mold-forming curable resin and is provided with a
recessed portion corresponding to a convex portion of the waveguide
core having a notched portion which includes an optical path
changing surface and two or more through holes which are
respectively communicated with one end and another end of the
recessed portion;
[0111] 2) a step of bringing a lower clad film having favorable
close contact characteristics with the mold into close contact with
the mold;
[0112] 3) a step of filling the through hole formed in one end of
the recessed portion of the mold which is brought into close
contact with the lower clad film with core-forming curable resin
and filling the recessed portion of the mold with the core-forming
curable resin by performing vacuum suction of the core-forming
curable resin from the through hole formed in another end of the
recessed portion of the mold;
[0113] 4) a step of curing the core-forming curable resin and
peeling off the mold from the lower clad film; and
[0114] 5) a step of stacking an upper clad film on the lower clad
film on which a core is formed.
[0115] The second method differs from the first method with respect
to a point that, as the mold, the second method uses the mold
having the recessed portion corresponding to the core convex
portion of the waveguide including the notched portion which has
the optical path changing surface. In this method, since the
portion which corresponds to the notched portion is already formed
in the mold, it is possible to provide a simple and convenient
method compared to the method in which the notched portion is
formed in every manufactured optical waveguide film as the final
step.
[0116] To manufacture the mold explained above, in the original
disc manufacturing step in the first method, the notched portion
may be formed in the convex portion of the original disc on which
the convex portion which corresponds to the waveguide core is
formed and the mold may be formed based on the original disc. As
the method for forming the notched portion, the notched portion
forming method in the step 6) of the above-mentioned first method
can be used in the same manner. Thereafter, the steps 2) to 5) in
the first method can be performed in the same manner to manufacture
the optical waveguide film in the present invention.
[0117] In the above-mentioned manufacturing method of the optical
waveguide film (the previously-mentioned first method), although
the step of forming the notched portion is necessary, basically, as
described above, by merely bringing the lower clad film which
exhibits the favorable close contact property with the mold into
close contact with the mold (unnecessary to fix both of them using
any particular unit), no gap is formed between the mold and the
clad substrate other than the recessed portion structure formed in
the mold and hence, the core-forming curable resin is allowed to
enter only the recessed portion. Accordingly, it is possible to
provide the simplified method in which the optical waveguide film
can be manufactured at a low cost. Further, in this method, the
through hole is formed in the mold and suction under the reduced
pressure is performed at the core-forming curable resin discharge
side of the mold recessed portion and hence, the close contact
property of the mold and the film substrate is further enhanced and
hence, the mixing of bubbles can be avoided. Accordingly, the
second method is characterized in that it is possible to obtain the
highly accurate optical waveguide film with the least waveguide
loss while ensuring the simple method.
[0118] Further, although it is necessary to form the notched
portion in the final step, the step per se is a step in which the
cutting operation using a dicing saw, for example, is performed
only one time and hence, the step is not cumbersome whereby the
formation of the notched portion does not damage the
characteristics of the optical waveguide film manufacturing method
which is simplified and convenient and can be performed at a low
cost.
[0119] The second manufacturing method which forms the notched
portion only in the core provides the further convenient method in
which it is sufficient to form the notched portion in the original
disc manufacturing step.
[0120] In the optical waveguide film of the present invention, it
is possible to form the optical path changing mirror surface
necessary for the planar mounting of the optical waveguide film on
the light emitting element such as the VCSEL or the like by the
cutting forming using the dicing saw in the same manner as the
usual end face. A technique on the dicing saw is, for example,
disclosed in Japanese Patent Laid-Open Publication No. Hei
10-300961.
[0121] The present invention is further explained specifically in
conjunction with the following embodiments. However, the present
invention is not limited by them.
First Embodiment
[0122] A thick film resist (product of MicroChem Corp., SU-8) is
applied to a Si substrate by a spin coating method, is then
pre-baked at a temperature of 80.degree. C., is exposed through a
photo mask, and is developed thus forming four optical waveguide
convex portions having a square cross section (width: 50 .mu.m,
height: 50 .mu.m, length: 50 mm, pitch: 250 .mu.m). Next, the
optical waveguide convex portions are post-baked at 120.degree. C.
to form the optical waveguide core manufacturing original
discs.
[0123] Next, after applying a mold removing agent to the original
disc, thermosetting dimethylcyclic resin (product of Dow Coning
Asia Corporation, SYLGARD184) is made to flow into the original
discs, is solidified by being heated at a temperature of
120.degree. C. for 30 minutes and is peeled off thus manufacturing
molds having recessed portions corresponding to optical waveguides
convex portions having the square cross section and the alignment
mark convex portions (thickness of mold: 5 mm).
[0124] Further, through holes having a diameter of 3 mm
respectively are formed in both ends of the recessed portion of the
mold to expose both ends of the recessed portion thus manufacturing
the mold in which inlet and outlet portions for ultraviolet ray
curable resin which are described below are formed.
[0125] The mold and a film substrate having a design film thickness
of 100 .mu.m one size larger than the mold (Arton film, product of
JSR Corporation, refractive index: 1.510) are prepared. The Arton
film and the mold are brought into close contact with each other.
Next, when several drops of ultraviolet ray curable resin having
the viscosity of 1300 mPas are dropped in the hole formed in each
end of the optical waveguide manufacturing recessed portion formed
in the mold and the hole is sucked with a suction force of 20 kPa
using a diaphragm suction pump (maximum suction pressure: 33.25
kPa), the ultraviolet ray curable resin is filled into each
recessed portion. Next, the resin is radiated with UV light of 50
mW/cm.sup.2 through the mold for 5 minutes thus curing the mold
with ultraviolet rays. When the mold is peeled off from the film
substrate, a core having the same shape as the convex portion on
the original disc is formed on the film substrate. The refractive
index of the core is 1.53. Cladding ultraviolet ray curable resin
having the refractive index of 1.51 and the Arton film having the
thickness of 100 .mu.m are applied to the core, they are radiated
with a UV light of 50 mW/cm.sup.2 for 10 minutes for curing the
clad-forming ultraviolet ray curable resin thus forming an optical
waveguide film having the sandwich structure which sandwiches the
core with the upper and lower Arton films. Further, the optical
waveguide film is cut to a width 2 mm using a dicing saw in a state
that the waveguide core is positioned at the center. Further, a
joining portion of the optical waveguide film with the optical
fiber is straightly cut in the direction orthogonal to the
waveguide core to expose a vertical mirror surface.
[0126] At a position spaced apart from the above-mentioned vertical
mirror surface by 25 mm, first of all, a 45.degree. mirror surface
for inputting a VCSEL light is formed. This forming operation is
performed by mounting a blade having a 45.degree. distal end on the
dicing saw. Further, at a position between the 45.degree. mirror
surface and the vertical mirror surface and 2 mm spaced apart from
the distal end of the 45.degree. mirror surface (the distal end
portion of optical waveguide film), a notch having the inclination
of 45.degree. is formed into the core from an upper surface of the
upper clad film in a state that a depth from an upper surface of
the core becomes 5 .mu.m.
[0127] A ceramic package is prepared and an 1.times.8 VCSEL
(product of Fuji Xerox Co., Ltd.) and a drive driver are mounted on
the ceramic package. In the vicinity of the VCSEL, an 1.times.8 PD
(photo detector for monitoring) is mounted on the ceramic package,
and an output from the PD is connected with a feedback port of the
drive driver.
[0128] The optical waveguide film is adhered to the VCSEL and the
PD using the clad-forming curable resin. Here, the adhering
operation is performed in a state that the position of the
45.degree. mirror surface corresponds to the VCSEL light emitting
surface and the position of the notched portion in the midst of the
core corresponds to the monitor PD. Further, on an end portion of
the optical waveguide film, a connector which is interchangeable
with the commercially available MT connector is mounted by adhesion
thus completing the optical module.
[0129] The insertion loss of the optical module is 2.8 dB using an
output of the VCSEL as the reference and the irregularities of the
insertion loss among respective ports can be suppressed within 0.2
dB.
[0130] Further, the stable output is ensured until an ambient
temperature is elevated to 80 degrees.
COMPARATIVE EXAMPLE 1
[0131] When the optical module having the same structure except for
that the optical module is not provided with the monitor PD is
manufactured, an output when the ambient temperature is elevated to
80 degrees becomes one tenth of the output when the temperature is
20 degrees.
Second Embodiment
[0132] A thick film resist (product of MicroChem Corp., SU-8) is
applied to a Si substrate by a spin coating method, is then
pre-baked at a temperature of 80.degree. C., is exposed through a
photo mask, is developed thus forming eight optical waveguide
convex portions having a square cross section (width: 50 .mu.m,
height: 50 .mu.m, length: 50 mm, pitch: 250 .mu.m). Next, the
optical waveguide convex portions are post-baked at a temperature
of 120.degree. C.
[0133] Thereafter, using a dicing saw which mounts a 45.degree.
blade, a notch having a depth of 10 .mu.m is formed from an upper
surface of each convex portion thus forming an original disc for
manufacturing the optical waveguide core (see the core shown in
FIG. 1C).
[0134] Next, after applying a mold removing agent to the original
disc, thermosetting dimethylcyclic resin (product of Dow Coning
Asia Corporation, SYLGARD184) is made to flow into the original
discs, is solidified by being heated at a temperature of
120.degree. C. for 30 minutes, and is peeled off thus manufacturing
molds having recessed portions corresponding to optical waveguides
convex portions having the square cross section and the alignment
mark convex portions (thickness of mold: 5 mm). Further, through
holes having a diameter of 3 mm respectively are formed in both
ends of the recessed portion of the mold to expose both ends of the
recessed portion thus manufacturing the mold in which inlet and
outlet portions for ultraviolet ray curable resin which are
described below are formed.
[0135] The mold and a film substrate having a design film thickness
of 100 .mu.m one size larger than the mold (Arton film, product of
JSR Corporation, refractive index: 1.510) are prepared. The Arton
film and the mold are brought into close contact with each other.
Next, when several drops of ultraviolet ray curable resin having
the viscosity of 130 mPas are dropped in the through hole formed in
one end of the optical waveguide manufacturing recessed portion and
the curable resin is sucked from the through hole formed in another
end of the recessed portion of the mold with a suction force of 20
kPa using a diaphragm suction pump (maximum suction pressure: 33.25
kPa), the ultraviolet ray curable resin is filled into each
recessed portion. Next, the resin is radiated with a UV light of 50
mW/cm.sup.2 through the mold for 5 minutes thus curing the mold
with ultraviolet rays. When the mold is peeled off from the film
substrate, a core having the same shape as the convex portion on
the original disc is formed on the film substrate. The refractive
index of the core is 1.59. Cladding ultraviolet ray curable resin
having the refractive index of 1.51 and the Arton film having the
thickness of 100 .mu.m are applied to the core, they are radiated
with a UV light of 50 mW/cm.sup.2 for 10 minutes for curing the
clad-forming ultraviolet ray curable resin thus forming an optical
waveguide film having the sandwich structure which sandwiches the
core with the upper and lower Arton films. Further, the optical
waveguide film is cut to a width 2.5 mm using a dicing saw in a
state that the waveguide core is positioned at the center. Further,
a joining portion of the optical waveguide film with the optical
fiber is straightly cut in the direction orthogonal to the
waveguide core to expose a vertical mirror surface. The position is
disposed 23 mm away from the notched surface formed in the
core.
[0136] At a position spaced apart from the above-mentioned vertical
mirror surface by 25 mm, a 45.degree. mirror surface for inputting
a VCSEL light is formed. The 45.degree. mirror surface is formed by
mounting a blade having a 45 degree distal end on a dicing saw.
[0137] A ceramic package is prepared and a 1.times.8 VCSEL (product
of Fuji Xerox Co., Ltd.) and a drive driver are mounted on the
ceramic package. In the vicinity of the VCSEL, an 1.times.8 PD
(photo detector for monitoring) is mounted on the ceramic package,
and an output from the PD is connected with a feedback port of the
drive driver.
[0138] The optical waveguide film is adhered to the VCSEL and the
PD using the clad-forming curable resin. Here, the adhering
operation is performed in a state that the position of the
45.degree. mirror surface corresponds to the VCSEL light emitting
surface and the position of the notched portion in the midst of the
core corresponds to the monitor PD. Further, on an end portion of
the optical waveguide film, a connector which is interchangeable
with the commercially available MT connector is mounted by adhesion
thus completing the optical module.
[0139] The insertion loss of the optical module is 3.2 dB using an
output of the VCSEL as the reference and the irregularities of the
insertion loss of respective ports can be suppressed within 0.2
dB.
[0140] Further, the stable output is ensured until an ambient
temperature is elevated to 80 degrees.
Third Embodiment
[0141] A thick film resist (product of MicroChem Corp., SU-8) is
applied to a Si substrate by a spin coating method, is then
pre-baked at a temperature of 80.degree. C., is exposed through a
photo mask, is developed thus forming eight optical waveguide
convex portions having a square cross section (width: 50 .mu.m,
height: 50 .mu.m, length: 50 mm, pitch of neighboring portions: 250
.mu.m). Next, the optical waveguide convex portions are post-baked
at a temperature of 120.degree. C.
[0142] Thereafter, the original disc is formed by forming notches
in the convex portions. As a dicing saw for forming the notches, a
dicing saw on which a vertical cutting blade having a thickness of
20 .mu.m is mounted is used. In a state that the Si substrate on
which eight convex portions are formed as described above is fixed
at an angle of 45.degree. with respect to the blade of the dicing
saw using a retaining jig, the notches are formed to a depth of 28
.mu.m from upper surfaces of the convex portions. Here, width of
the notches is set to 23 .mu.m.
[0143] Next, after applying a mold removing agent to the original
disc, thermosetting dimethylcyclic resin (product of Dow Coning
Asia Corporation, SYLGARD184) is made to flow into the original
discs, is solidified by being heated at a temperature of
120.degree. C. for 30 minutes and is peeled off thus manufacturing
molds having recessed portions corresponding to optical waveguides
convex portions having the square cross section and the alignment
mark convex portions (thickness of mold: 5 mm).
[0144] Further, through holes having a diameter of 3 mm
respectively are formed in both ends of the recessed portion of the
mold to expose both ends of the recessed portion thus manufacturing
the mold in which inlet and outlet portions for ultraviolet ray
curable resin which are described below are formed.
[0145] The mold and a film substrate having a design film thickness
of 100 .mu.m one size larger than the mold (Arton film, product of
JSR Corporation, refractive index: 1.510) are prepared. The Arton
film and the mold are brought into close contact with each other.
Next, when several drops of ultraviolet ray curable resin having
the viscosity of 1300 mPas are dropped in the through hole formed
in one end of the recessed portion of the mold and the curable
resin is sucked from the through hole formed in another end of the
mold recessed portion with a suction force of 20 kPa using a
diaphragm suction pump (maximum suction pressure: 33.25 kPa), the
ultraviolet ray curable resin is filled into each recessed portion.
Next, they are radiated with a UV light of 50 mW/cm.sup.2 through
the mold for 5 minutes thus curing the mold with ultraviolet rays.
When the mold is peeled off from the film substrate, a core having
the same shape as the convex portion on the original disc is formed
on the film substrate. The refractive index of the core is 1.59.
The Arton film having the thickness of 100 .mu.m is stacked on the
core by way of the clad-forming ultraviolet ray curable resin
(adhesive agent) having the refractive index of 1.51, and they are
radiated with a UV light of 50 mW/cm.sup.2 for 10 minutes for
curing the clad-forming ultraviolet ray curable resin thus forming
an optical waveguide film having the sandwich structure which
sandwiches the core with the upper and lower Arton films. Further,
the optical waveguide film is cut to a width 2.5 mm using a dicing
saw in a state that the waveguide core is positioned at the center.
Further, a joining portion of the optical waveguide film with the
optical fiber is straightly cut in the direction orthogonal to the
waveguide core to expose a vertical mirror surface. The position is
disposed 23 mm away from the notched surface formed in the
core.
[0146] At a position spaced apart from the above-mentioned vertical
mirror surface by 25 mm, a 45.degree. mirror surface for inputting
a VCSEL light is formed. The 45.degree. mirror surface is formed by
mounting a blade having a 45 distal end on a dicing saw.
[0147] A ceramic package is prepared and a 1.times.8 VCSEL (product
of Fuji Xerox Co., Ltd.) and a drive driver are mounted on the
ceramic package. In the vicinity of the VCSEL, an 1.times.8 PD is
mounted on the ceramic package, and an output from the PD is
connected with a feedback port of the drive driver.
[0148] The optical waveguide film is adhered to the VCSEL and the
PD using the clad-forming curable resin. Here, the adhering
operation is performed in a state that the position of the
45.degree. mirror surface corresponds to the VCSEL light emitting
surface and the position of the notched portion in the midst of the
core corresponds to the monitor PD. Further, on an end portion of
the optical waveguide film, a connector which is interchangeable
with the commercially available MT connector is mounted by adhesion
thus completing the optical module.
[0149] The insertion loss of the optical module is 2.8 dB using an
output of the VCSEL as the reference and the irregularities of the
insertion loss of respective ports can be suppressed within 0.2
dB.
[0150] Further, the stable output is ensured until an ambient
temperature is elevated to 80 degrees.
[0151] As described above, according to an aspect of the present
invention, an optical waveguide module includes a light emitting
element which outputs light, a light receiving element which
monitors an output of the light emitting element and an optical
waveguide film having a waveguide core in the optical waveguide
film which has a notched portion having an optical path changing
surface that changes an optical path of part of the light. The
light emitting element is coupled to an end portion of the optical
waveguide film, and the light receiving element is provided to face
a position of the optical waveguide film from where the part of the
light whose optical path has been changed by the optical path
changing surface exits.
[0152] The light emitting element may be a surface emitting type
light emitting element, the optical waveguide film may have an
optical path changing mirror surface on one end portion thereof,
and light emitted from the surface emitting type light emitting
element may be coupled to the waveguide by way of the mirror
surface.
[0153] The optical path changing mirror surface may be a 45.degree.
mirror surface formed by cutting the optical waveguide film with a
dicing saw provided with a 45.degree. blade.
[0154] The notched portion may be exposed to air. Alternatively,
the notched portion may be filled with a cured material of
ultraviolet ray curable resin.
[0155] The optical path changing surface may be a surface inclined
at an angle of approximately 45.degree..
[0156] The surface inclined at an angle of approximately 45.degree.
may be formed by cutting the optical waveguide film with a dicing
saw provided with a vertical cutting blade which is allowed to have
the inclination of approximately 45.degree. with respect to the
optical waveguide film.
[0157] According to another aspect of the invention, an optical
waveguide film includes a lower clad film, a waveguide core having
a notched portion having an optical path changing surface at a
portion thereof and an upper clad film.
[0158] According to another aspect of the invention, a
manufacturing method of an optical waveguide film includes the
steps of preparing a mold which is formed of a cured layer of a
mold-forming curable resin and is provided with a recessed portion
corresponding to a protruding portion of the waveguide core and two
or more through holes which are communicated with respective ends
of the recessed portion, bringing a lower clad film into close
contact with the mold, filling one of the through holes formed to
communicate with one end of the recessed portion of the mold with
core-forming curable resin, the mold being brought into close
contact with the lower clad film, and filling the recessed portion
of the mold with the core-forming curable resin by performing
vacuum suction of the core-forming curable resin from the through
hole formed to communicate with another end of the recessed portion
of the mold, curing the core-forming curable resin and peeling off
the mold from the lower clad film, forming a notched portion at a
portion of the waveguide core, the notched portion having an
optical path changing surface, and forming an upper clad film on
the lower clad film on which a core is formed.
[0159] According to another aspect of the invention, a
manufacturing method of an optical waveguide film includes
preparing a mold which is formed of a cured layer of a mold-forming
curable resin and is provided with a recessed portion corresponding
to a protruding portion of the waveguide core having a notched
portion which includes an optical path changing surface and two or
more through holes communicated with respective ends of the
recessed portion, bringing a lower clad film into close contact
with the mold, filling one of the through holes formed to
communicate with one end of the recessed portion of the mold with
core-forming curable resin, the mold being brought into close
contact with the lower clad film, and filling the recessed portion
of the mold with the core-forming curable resin by performing
vacuum suction of the core-forming curable resin from the through
hole formed to communicate with another end of the recessed portion
of the mold, curing the core-forming curable resin and peeling off
the mold from the lower clad film, and forming an upper clad film
on the lower clad film on which a core is formed.
[0160] With the optical waveguide module according to some aspects
of the present invention, by merely arranging the optical waveguide
film in which the specific notched portion is formed in the
waveguide core in a light receiving element for monitoring which
monitors the light emitting element and an output of the light
emitting element, it is possible to monitor the output of the light
emitting element and hence, steps such as the alignment of micro
lenses which has been necessary in the related art is no more
necessary. Further, in the optical waveguide module of the present
invention, it is sufficient to couple the light emitting element to
the end portion of the optical waveguide film and hence, it is
unnecessary to use the particularly prepared mirrors, lenses and
the like. Accordingly, the optical waveguide module of the present
invention ensures the easy mounting and, at the same time, has the
simple structure thus realizing the manufacture of the optical
waveguide module at an extremely low cost. Further, the mounted
module is also extremely compact.
[0161] Further, the optical waveguide film per se used in the
optical waveguide module can be also manufactured using the simple
method and hence, the increase of steps for forming the notched
portion can be minimized and hence, it is also possible to
manufacture the optical waveguide film at a low cost.
[0162] Still further, when the waveguide cores of the optical
waveguide film are provided in plural number, monitor light can be
taken out independently from each waveguide core without affecting
other cores and hence, the monitor light from each core accurately
reflects the output of the light emitting point whereby the
feedback by monitoring can be accurately performed. As a result, it
is possible to ensure the uniform outputting from a distal end of
each core. Further, although there exists the possibility that the
waveguide loss is generated due to the intersection caused by
branching the core in the related art. However, some aspects of the
present invention has no possibility of generating such a waveguide
loss and hence, the outputs of respective cores can be made
uniform.
[0163] The foregoing description of the embodiments of the present
invention has been provided for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Obviously, many
modifications and variations will be apparent to practitioners
skilled in the art. The embodiments were chosen and described in
order to best explain the principles of the invention and its
practical applications, thereby enabling others skilled in the art
to understand the invention for various embodiments and with the
various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
[0164] The entire disclosure of Japanese Patent Application No.
2004-193847 filed on Jun. 30, 2004 including specification, claims,
drawings and abstract is incorporated herein by reference in its
entirety.
* * * * *